Atomic origins of the surface components in the Si 2pcore-level spectra of the Si(111)7×7 surface

The 7×7 surface has been studied with Si 2p core-level spectroscopy using an experimental resolution better than 70 meV at a temperature of 120 K. The spectra are much more well resolved than earlier reports and provide considerably more information. They consist of a bulk component and five surface components, three of which appear as peaks or shoulders in the spectra. We find that the component that is shifted 0.70 eV to lower binding energies (${\mathit{S}}_2$) is due to the rest atoms. The contribution from the adatoms is revealed by a component, twice as large as ${\mathit{S}}_2$, shifted 0.53 eV to higher binding energies.